The commonly used household electric appliances often occur malfunction due to unstable DC power. Some areas have great voltage fluctuations that even cause damages of the electric appliances and result in huge losses to users. It is widely recognized that stability of electricity is important. Hence many venders have developed voltage regulators to stabilize electric power supply. The voltage regulators often are formed in an independent structure which contains an iron core transformer to connect to a circuit. They usually are separately installed on the electric appliances or extension lines or sockets. Operation is quite troublesome. Moreover, conventional iron core transformers generally have a bulky size and take a large space. It is against the prevailing trend that focuses slim and light. In addition, the conventional voltage regulators tend to overheat after having operated under full load for a long period of time. This impacts the service life of the voltage regulator, or indirectly affects normal operation for a given load.
Thus to resolve the problem of bulky conventional voltage regulators caused by the iron core transformers and develop slim and light voltage regulators to increase convenience of product utilization are an important issue remained to be overcome.